Color organ tiki-o’-lantern

The Halloween parties this weekend are over, but that doesn’t mean there’s not time for a few more to finish a build before children start knocking on doors tonight. [formori] at Lakehead University wanted to do something spectacular for a pumpkin carving contest, so he and a few other EE students came up with a tiki-o’-lantern with music.

The guys at Lakehead figured a color organ flashing LEDs in the eyes and mouth of the tiki would be a very good and easy project. The circuit they used is a simple Op-amp setup like one we’ve seen earlier. The entire pumpkin is powered by a 9 V battery and the music is played with an iPod. There are two colors of LEDs – high frequencies flash a blue LED in the eyes and low frequencies flash a red LED in the mouth.

Aside from the added A/V stuff, [formori]’s pumpkin is one of the best we’ve seen on Hack a Day this year. Check out the Youtube of 1st place winner of the Lakehead pumpkin carving contest after the break.

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7 thoughts on “Color organ tiki-o’-lantern”

Very cool. Now that you said it’s one of the best pumpkins you’ve seen on HAD, be prepared for a flood of “mine’s better!”

Here’s mine… not better but similar.

I fashioned my own carving tools out of xacto knife handles and scraps of thin steel that I bent into the shape of an ‘L’ and put a sharp edge on it with a dremel. Not ideal… but next year I’ll get some real tools because carving is fun.

Interesting stuff, I have been looking at making a color organ (as these are called) myself, since learning about filters in DC/AC class.

We are moving on to op-amps and active filters now. I have a question for anyone here about the schematic in the link “one we’ve seen earlier”. The guy seems to be amplifying the input signal and then filtering it, whereas my textbook shows the filter as being part of the circuit input. What’s the difference?

Also, how does one know the output impedance of their mp3 player or other devices without loading it and measuring voltage drop?

Well, with regard to the filters, you can do it either way. You can setup the op-amp filtering on chip (requires more components, but gives cleaner output) or just amplify and filter the signal (less components but more noise), so it’s up to you.

And the impedance for most if around 100ohms (I used my 3G video iPod and some 100ohm input resistors for this), anything close will work, as long as the feedback on the amp is matched.

Just a note, I wish I had better carving tools when doing this, I only had an exacto knife and a small paring knife!

“as long as the feedback on the amp is matched”. Just for clarity, are you just saying that the amp gain should be enough to create a full-size signal for the output, or is there something to consider with regards to amp gain and input impedance?